Ed Balls, the shadow chancellor, faced calls on Monday night to return a £50,000 donation linked to a former bank chief accused of buying class A drugs.

The Conservatives highlighted connections between Mr Balls and the Rev Paul Flowers, the former chairman of the Cooperative Bank.

Mr Flowers, 63, a Methodist minister and former Labour councillor, has been suspended from the party after film footage apparently showed him discussing the purchase of crystal meth, cocaine and ketamine. He was said to have bought drugs days after giving evidence to the Commons Treasury committee on how the bank lost £700 million.

In March 2012, Mr Balls’s office received a donation worth £50,000 from the Co-op Group. As chairman of the bank, Mr Flowers was a director of the group at the time. In his evidence to MPs, Mr Flowers confirmed that he had been involved in a decision to give financial support to Mr Balls’s office.

Brooks Newmark, a Tory member of the committee, said: “The Rev Flowers’s judgment was clearly impaired if he was prepared to give Ed Balls £50,000. Mr Balls should now ask himself whether it is right to accept that money, and consider giving it back.”

A spokesman for Mr Balls said: “This was a donation from the Co-op Group, not the bank. We never discussed it with the Rev Flowers and it was declared in the Register of Members’ Interests.”